With the continued miniaturization of integrated circuit (“IC”) devices, the current trend is to produce integrated circuits having shallower junction depths, thinner gate oxides, lightly-doped drain (“LDD”) structures, shallow trench isolation (“STI”) structures, and self-aligned silicide (“salicide”) processes, all of which are used in advanced sub-quarter-micron complementary metal oxide semiconductor (“CMOS”) technologies. All of these processes cause the related CMOS IC products to become more susceptible to damage due to ESD events. Therefore, ESD protection circuits are built onto the chip to protect the devices and circuits on the IC from ESD damage.
As semiconductor processing technology advances, the gate dielectric of MOS transistors becomes thinner and increasingly susceptible to damage caused by ESD current. This issue becomes more serious when the MOS transistor is used in a multi-power domain circuitry. where a diode module is typically connected to an I/O ground bus between two power domains. When the ESD occurs, the diode module may induce the ESD current to flow through a damaging path other than the I/O ground bus as a desired path, thereby damaging the thin-gate-dielectric MOS transistors.
According to the ESD Association's Charge Device Model (CDM) roadmap, with the advent of larger capacitance IC packages, the higher capacitance will lead to relatively higher magnitude discharge peak current levels, creating new challenges.